Metallurgical Source of Cryogenic Intergranular Fracture of Fe-38Mn Austenitic Alloy  

作　　者：FU Rui-dong ZHENG Yang-zeng LI Shao-hua ZHOU Hui-hua 

机构地区：[1]Yanshan University [2]Central Iron & Steel Research Institute [3]Tsinghua University

出　　处：《Journal of Iron and Steel Research International》2000年第1期31-35,共5页

基　　金：Project Sponsored by National Natural Science Foundation(59771001)

摘　　要：SEM and Field emitting TEM-EDAX were used to investigate the fracture surface of series impact specimens and the grain boundary chemistries of VIM(vacuum-inductionmelted) Fe-38 Mn austenitic alloy before and after ESR(electroslag remelting,).The quantity and the size of inclusions were also examined.The results show that the VIM Fe-38 Mn austenitinic alloy water-quenched from 1 100 C undergoes an obvious ductile-to-brittle transition,and the impact work at ambient temperature is 242 J,the corresponding fracture surface exhibits a dimple character.However,the impact work at 77 K of VIM alloy is only 25 J and the fracture mode is IGF(intergranular fracture).After ESR,the impact work at ambient temperature is 320 J and the fracture surface exhibits a character of "volcano lava"(meaning excellent toughness);The impact work at 77 K is up to 300 J and the fracture mode is micro void coalescence mixed with quasi-cleavage.The segregation of Mn is not found in all specimens,but the segregation of S is observed,and the S segregation is decreased after ESR.The examined results of inclusions show that ESR reduces the quantity and improves the morphology of inclusions.From the above results it can be seen that the cryogenic IGF of VIM Fe-38 Mn austenitic alloy is related to the S segregation at grain boundary.After ESR the decrease in the quantity and size of inclusion results in the increase of the impact work at ambient temperature,while the restriction of IGF is related to the decrease in the total level,and hence in the grain boundary segregation of S.SEM and Field emitting TEM-EDAX were used to investigate the fracture surface of series impact specimens and th e grain boundary chemistries of VIM (vacuum-induction-melted) Fe-38Mn austeni tic alloy before and after ESR (electroslag remelting,). The quantity and the si ze of inclusions were also examined. The results show that the VIM Fe-38Mn aust enitinic alloy water-quenched from 1 100 ℃ undergoes an obvious ductile-to-b rittle transition, and the impact work at ambient temperature is 242 J, the corr esponding fracture surface exhibits a dimple character. However, the impact work at 77 K of VIM alloy is only 25 J and the fracture mode is IGF (intergranular f racture). After ESR, the impact work at ambient temperature is 320 J and the fra cture surface exhibits a character of “volcano lava” (meaning excellent toughn ess); The impact work at 77 K is up to 300 J and the fracture mode is microvoid coalescence mixed with quasi-cleavage. The segregation of Mn is not found in al l specimens, but the segregation of S is observed, and the S segregation is decr eased after ESR. The examined results of inclusions show that ESR reduces the q uantity and improves the morphology of inclusions. From the above results it can be seen that the cryogenic IGF of VIM Fe-38Mn austenitic alloy is related to t he S segregation at grain boundary. After ESR the decrease in the quantity and s ize of inclusion results in the increase of the impact work at ambient temperatu re, while the restriction of IGF is related to the decrease in the total level, and hence in the grain boundary segregation of S.

关 键 词：rich Mn austenitic alloy cryogenic intergranular fracture grain boundary segregation electroslag remelting 

分 类 号：TG115[金属学及工艺—物理冶金]